Re: [RFC PATCH 02/20] x86/sgx: Store EPC page owner as a 'void *' to handle multiple users

[Dave Hansen]

On 9/22/22 10:10, Kristen Carlson Accardi wrote:
> From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> 
> A future patch will use the owner field for either a pointer to
> a struct sgx_encl, or a struct sgx_encl_page.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> Signed-off-by: Kristen Carlson Accardi <kristen@xxxxxxxxxxxxxxx>
> Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/sgx/sgx.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/sgx.h b/arch/x86/kernel/cpu/sgx/sgx.h
> index 0f2020653fba..5a7e858a8f98 100644
> --- a/arch/x86/kernel/cpu/sgx/sgx.h
> +++ b/arch/x86/kernel/cpu/sgx/sgx.h
> @@ -33,7 +33,7 @@ struct sgx_epc_page {
>  	unsigned int section;
>  	u16 flags;
>  	u16 poison;
> -	struct sgx_encl_page *owner;
> +	void *owner;
>  	struct list_head list;
>  };
>  

We normally handle these with a union.  I'd probably do something like
this instead:

-	struct sgx_encl_page *owner;
+	union owner {
+		struct sgx_encl	     *o_encl;
+		struct sgx_encl_page *o_page;
+	}